Highly active herbicidal compounds of the class constituting aryloxyphenoxyalkanoic, and aryloxyphenoxy. alkenoic acids and related compounds have been described in the patent literature. These compounds have been prepared by making derivatives of the acid function thereof and bearing various groups or substituents on, primarily, the aryl structure. Such compounds in which the aryloxy and O-alkanoic acid functions respectively are disposed in 1,4 relation on the phenyl group, are especially active against grassy, i.e., gramineous weeds while displaying little or no herbicidal activity against broadleaf plants and, often, only slight activity against cereal grains. However, these compounds as a group are generally injurious to corn, i.e., maize, and are of little use for controlling grassy weeds in corn crops.